Question

(a – b) = 3 and ab = 5 then a³ – b³ = __________

विकल्प

• 15

• 18

• 62

• 72

Answer 1

72

Explanation;

Hint:

(a – b) = 3

(a – b)² = 3²

a² + b² – 2ab = 9

a² + b² – 2(5) = 9

a² + b² = 9 + 10

a² + b² = 19

a³ – b³ = (a – b)(a² + ab + b²)

= 3(19 + 5)

= 3(24)

= 72